The present invention relates to air conditioning service valves and more particularly to service valve and stem cap designs.
Residential and commercial air conditioning systems include a service valve for charging and/or bleeding refrigerant contained within the air conditioning system. In these systems, the service valve is typically opened and closed by manually adjusting a valve stem inwardly or outwardly within a valve body cavity. The valve stem is typically housed within and threadably engages the valve body so that when the valve stem is rotated about its longitudinal axis, the valve stem moves inwardly or outwardly depending upon the direction of the rotation. A service valve sealing cap engages the outside of the valve body and encapsulates the valve stem cavity to prevent ingress of harmful debris or moisture.
The refrigerant within air conditioning systems may exert high pressures upon the valve stem and upon the valve body. The internal high pressure of the refrigerant may force the valve stem out of the valve body, leading to both loss of refrigerant and potential loss of the valve stem. In particular, if the service personnel rotates the valve stem sufficiently outwardly so that the threads on the exterior valve stem disengage from the threads on the interior of the valve body cavity, the force on the valve stem due to the high pressure refrigerant may push the valve stem from the valve body. If the valve stem becomes lost or if the refrigerant escapes, then any service operation becomes more complex and potentially more expensive to carry out, especially if the valve stem becomes lost and requires replacement.
Various methods have been developed to prevent escape of the valve stem. For instance, structural valve stem retention features may be built into the valve body to limit the outward movement of the valve stem. However, some of these structural features, such as snap rings, may be removed or disengaged by the service personnel, who may then neglect to replace the structural features, thereby disabling the features designed to retain the valve stem within the valve body. Thus, manufacturers of such service valves desire permanent non-removable retention features that prevent removal or separation of the valve stem from the valve body. Additionally, once a service person replaces the service valve cap, it is impossible to tell if the retention features have been removed.
Likewise, during manufacture, it is often difficult during manufacture to ascertain that each and every service valve produced includes all the structural retention features without performing a costly and time-consuming visual inspection of each part. Thus, manufacturers also desire readily visible indicators that all structural retention features are included and installed on any service valve produced.
The present invention is directed to a service valve and cap assembly whereby a manufacturer and an installer may readily ascertain that structural valve stem retention features exist that will prevent the separation of a valve stem from a valve body. The service value comprises a valve stem having a first radial outer diameter that is threadably inserted into a valve body cavity having a first inner diameter corresponding to the first outer diameter. An upper portion of the valve body defines a collar selectively formable between an installation position and a retained position, where the installation position inner diameter is substantially equivalent to the first inner diameter, and the retention position inner diameter is less than the first inner diameter. The collar also defines respective first and second collar outer diameters, depending upon the collar position. Lastly, the collar top extends a first distance longitudinally above a first attachment mechanism formed on the exterior surface of the valve body.
The valve body further includes exterior threads to receive a sealing cap to encapsulate the valve stem and the collar. The sealing cap includes a base portion and a sealing portion longitudinally extending from the base portion. The sealing portion inner surface further includes a second attachment mechanism for engagement with the corresponding first attachment mechanism on the exterior of the valve body. The threads are located a longitudinal second distance from the base portion, where the second longitudinal distance is greater than the first longitudinal distance between the collar top and the exterior attachment mechanism. The sealing portion inner surface also includes an annular shoulder formed between the top of the threads and the base portion that defines a shoulder inner diameter. The shoulder inner diameter is less than the first collar outer diameter, and is greater than the second collar outer diameter. During manufacture, after the valve stem is inserted into the cavity, the collar is compressed from the installation position to the retention position. In this way, the valve stem is structurally prevented from becoming separated from the valve body because the retention position inner diameter is less than the outer diameter of the valve stem. The compression of the collar also reduces the collar outer diameter to the second collar outer diameter which is less than the shoulder inner diameter. Lastly, the compression of the collar reduces the longitudinal extent that the collar projects above the first attachment mechanism, thereby allowing first and second attachment mechanisms to interact and lock the cap onto the valve body. Likewise, if the collar is not compressed, then the shoulder inner diameter is smaller than the first collar outer diameter, and the collar height is not reduced, so that the cap and valve body attachment mechanisms will not engage As a result, an uncompressed collar in the installation position interferes with the shoulder portion and the sealing cap base portion, thereby preventing installation of the sealing cap.
As long as the collar is compressed, thereby ensuring positive retention of the valve stem, the sealing cap may be installed. Additionally, if a sealing cap is installed, then the manufacturer may be assured that the compressed collar will prevent separation of the valve stem from the valve body. However, if the collar is not compressed, the sealing cap will not fit over the collar, thereby providing a simple visual verification that the valve stem is not structurally retained within the valve body. The manufacturer and the service personnel are thereby made aware if the valve body does not provide sufficient structural support to prevent loss of refrigerant and separation of the valve stem from the valve body.